Low speed,high torque rotary hydraulic motor

ABSTRACT

A hydraulic motor has a rotor with radial cylinders in which reciprocate pistons having axial ducts therethrough from end to end. The rotor is sandwiched between two stator plates which are anchored between opposite ends of a casing, but which float between the casing and the rotor sides. Flow abutments anchored to the stator plates divide an expansion chamber into three arcuate segments, beneath which the pistons retract. The rotor is driven by the force of pressure fluid fed through the duct in one piston to the expansion chamber defined between a just-passed abutment and the next-preceeding and then-extended piston. The pistons are fluid-driven, and guided by a cam slots in the stator plates.

1 51 Aug. 8, 1972 [54] LOW SPEED, HIGH TORQUE ROTARY HYDRAULIC MOTOR [72] Inventor: Michael DAmato, 112 North Dunbar Avenue, Waukesha, Wis. 53186 [22] Filed: Nov. 4, 1970 [21] Appl. No.: 86,700

[52] US. Cl. ..4l8/l73, 418/174, 418/184, 418/261 [51] Int. Cl ..F03c 3/00, F04c 17/00 [58] Field of Search ..418/184, 260, 131

[56] References Cited UNITED STATES PATENTS 983,754 2/1911 Nichols ..4l8/l84 1,597,542 8/1926 Polsley ..418/ 184 2,389,709 11/1945 Anders ..9 1/ 197 2,473,309 6/1949 Stephens ..4l8/127 2,475,224 7/ 1 949 Dietrickson ..418/184 2,636,480 4/1953 Beckers ..418/260 3 ,398,698 8/1968 Eickmann ..417/273 3,527,262 9/ 1970 Fuchs ..4l8/ 184 1,259,857 3/1918 Haga ..4 1 8/1 73 FOREIGN PATENTS OR APPLICATIONS 548,652 l/l923 France ..4 1 8/1 84 Primary ExaminerWilliam L. Freeh Attorney-James H. Littlepage ABSIRACT A hydraulic motor has a rotor with radial cylinders in which reciprocate pistons having axial ducts therethrough from end to end. The rotor is sandwiched between two stator plates which are anchored between opposite ends of a casing, but which float between the casing and the rotor sides. Flow abutments anchored to the stator plates divide an expansion chamber into three arcuate segments, beneath which the pistons retract. The rotor is driven by the force of pressure fluid fed through the duct in one piston to the expansion chamber defined between a just-passed abutment and the next-preceeding and then-extended piston, The pistons are fluid-driven, and guided by a cam slots in the stator plates.

17 Claims, 6 Drawing Figures PATENTEBAuc 8 m2 SHEET 1 0F 3 FIG 4 O mwmm m JM IN-JENTOR MICHAEL D AMATO ATTORNLY LOW SPEED, I-HGH TORQUE ROTARY HYDRAULIC MOTOR FIELD OF INVENTION Rotary Expansible Chamber Devices PRIOR ART Nichols US. Pat. No. 983,754; Anders US. Pat. No. 2,389,709; Stephens US. Pat. No. 2,473,309; Hydraulic Handbook, 3d Edition, Trade & Technical Press, Morden Surrey, England, Pages 230-232.

OBJECTS The primary object of this invention is to provide a rotary hydraulic motor capable of operating at low speed with high, uniform torque, and without cogging, pulsing, or being subject to stalling at any point. Another object is to provide a motor which is capable of being reversed by reversing the flow of oil thereto, and which is characterized by its ability to pump when it over-runs the drive of the oil being pumped into it, thereby providing braking capability.

In hydraulic motors of this type, several basic problems are usually encountered, a major one resulting from the difficulty in sealing the expansible chamber. An object now is to provide, in a motor which is divided into three equal segments and hence is capable of operation as three motors, a flow abutment in an annular trepan chamber between each segment, which flow abutrnents prevent oil from flowing around the chamber, and which serve as fixed ends of the expansion chambers.

Another problem frequently encountered results from axial unbalance in the fluid pressures exerted on the rotor. To avoid this, it is proposed now to provide a disc-shape rotor with opposed radial grooves, i.e., cylinders, in its opposite faces, in which cylinders the pistons reciprocate. Thus, whatever axial pressures are exerted on the rotor are equal and opposite, and hence there is no tendency of either the rotor or the pistons to cock or bind.

Another object is to provide a motor which, even though it is divided into three segments and normally operates at high torque and with large displacement for its physical size, is provided with a removable port end cover which is capable, by replacement with another cover with different porting, or by valving, of channeling the high pressure input oil and the low pressure return oil to an from all three sectors, to two sectors (for medium speed, lower torque) or to one sector only (for highest speed, lowest torque). While the details of only one port end cover (wherein all three sectors are active) are the subject of this application, one relevant feature is the provision, in the face of the stator plate against which the port plate faces, of pressure pads. Thus, the internal hydraulic pressures which tend to spread the casing of the motor apart in the axial direction, are balanced by the pressures exerted on the stator plate by the high-pressure oil in the pads. Hence, the pressures which otherwise would cause increase on the clearance between the rotor and case are counterbalanced, and thus excessive leakage and loss of efficiency is avoided.

Another problem usually encountered in a motor of this type has to do with the driving of the pistons.

Where this is done mechanically, the structure becomes massive, complicated, and subject to great wear. The object here is to provide for the drive of the pistons solely by hydraulic forces; and, while cam slots are used, these serve only to limit the movements of the pistons, both during their extension and retraction strokes, so that the pistons are precisely positioned radially at all times.

Still another problem usually encountered in motors of this general type results from the internal pressures which tend to force the stator faces away from the rotor faces and thereby create excessive leakage. To avoid this, it is intended now to provide stator plates which, although they are anchored to the casing and cannot rotate with the rotor, nevertheless have some freedom of movement in the axial direction of the rotor, so that they float between the casing and the rotor. By providing pressure pads on the sides of the stator plates which face the respective casing ends, and by ducting pressure fluid to the pads, and by utilizing leakage fluid, not only is there provided a good seal between the stator plates and the rotor, but also there results a good fully lubricated hydrostatic bearing.

These and other objects will be apparent from the following specification and drawings, in which:

FIG. 1 is an elevation of the port cover end of the motor;

FIG. 2 is a cross section along the line 22 of FIG. 1;

FIG. 3 is a cross section along the line 33 of FIG. 2, with parts broken away, and with two pistons removed;

FIG. 4 is a fragmentary cross section along the line 4-4 of FIG. 3;

FIG. 5 is an exploded perspective view showing one side of a fluid abutment and its retaining pin; and,

FIG. 6 is a perspective view of the other side of a flow abutment.

Referring now to the drawings in which like reference numerals denote similar elements, the rotary hydraulic motor 2 has a casing 4 composed of a port end cover 6 and a drive end cover 8 separated by a spacer ring 10. The casing parts are held together by through bolts 12 and accurately positioned by conventional dowels 14. Closely fitting between two stator plates l6r and 16f, later described, is a rotor 18 keyed as at 20 onto a drive shaft 22 rotatably supported in the cover plates by tapered bearing 24 and 26. A cap plate 27 on the cover plate holds the bearings in proper compression, shims being used if necessary. Seals 28 at the opposite ends of drive shaft 22 prevent leakage of oil to the exterior.

Referring particularly to FIG. 2, 3 and 4, it will be apparent that the rotor 18 has front and rear faces 18f and l8r which are identical to one another and, hence, the elements on only one face will be described, it being understood that the description applies to both faces. Radiating outwardly in the rotor faces are radial grooves 30, which, in the embodiment illustrated, are eleven in number in each face. The radially inward ends of grooves 30 are connected by cross bores 32 so that, as will be later apparent, when pressure fluid is supplied to the inner end of a radial groove in rear face l8r, the fluid is supplied with equal pressure to the inner end of the opposite radial groove in front face 18f and, of course, return fluid flows equally from the inner ends of the opposite grooves.

Sliding in radial grooves 30 are pistons 34. While these pistons are identical, a series of four of them will be designated 34a, 34b, 34c and 34d for purposes of exposition. In the inner faces of the front and rear stator plates 16f and l6r are undulating guide tracks 36. These are not earn tracks in the sense that they drive the pistons, but, rather, they serve as restrains on the pistons which are forced radially inwardly and outwardly entirely by fluid pressure. The pistons are guided in tracks 36 by means of bearing members, i.e., balls 38. Extending axially throughout the lengths of the pistons are ducts 40 which, as will be apparent from FIGS. 2 and 4 provide fluid communication from the inner ends of radial grooves to the trepan chambers, which are constituted by annular grooves 42 in the opposite faces of rotor 18.

Disposed in the grooves 42 on each side of rotor 18 are three flow abutments 44, the details of which are shown best in FIGS. and 6. The flow abutments are generally arcuate strips which fit closely in the annular grooves 42, and are anchored to the stator plates by means of pins 46. These flow abutments have arcuate radial outer and inner sides 50 and 52, respectively, flat inner faces 54 (i.e., the faces towards the stator plate to which they are pinned), and flat outer faces 56 (i.e., the faces disposed towards the rotor, and which slide against the inner side of grooves 42). As detailed in FIG. 6, the outer faces 56 have coves 58 formed thereon to provide additional surface areas and pockets so that pressure fluid will force the flow abutments 44 against their respective stator plates and balance against radially outward fluid pressure. The flow abutments 44, while having slight freedom of radial motion so that they will ride easily in the annular grooves and will not bind against the rotor if it has slight radial play, are anchored against circular motion by means of the pins 46 which fit in suitable holes 45 therefor in the stator plates. The pins have rectangular heads 47 which slide in grooves 48 in the flow abutments.

The ends of flow abutments 44 are beveled as indicated at 60, 62. There are three flow abutments 44 which divide the expansion chamber, i.e., groove 42, into three parts, which, by appropriate porting, can be charged with pressure fluid simultaneously or, if desired, only two of the parts may be charged or, in some instances, only one port may be charged.

As shown best in FIG. 3, disposed around the inner faces of stator plates 16f and l6r are pairs of oppositely directed L-shape alcoves 64a and 64b. The alcoves are identical, each comprising a radial inwardly extending stem 66 and a laterally extending arm 68. However, the alcoves constituting each pair are oppositely directed.

Disposed radially inward from alcoves 64a, and registering with the inner ends of radialy grooves 30 are ports 70 which, for differentiation, will be designated 70a, 70b and 700 which for purposes of exposition will be assumed to be pressure fluid inlet ports. Disposed radially inward from alcoves 64b are ports 72 which for convenience of this description will be designated 72a, 72b and 720 and which, by the same token, will be assumed to be low pressure return fluid ports. Assuming counterclockwise motion of the rotor as seen in FIG. 3, it is noteworthy that, when a groove with a piston such as piston 34b is in full registry with an inlet port, such as port 70a, the outer end of that groove lies opposite an alcove 64a; and when the inner end of the groove accommodating piston 34d has fully registered over an outlet port, such as port 72a, the outer end of such groove has arrived over alcove 64b. The shapes of alcoves 64a and 64 b provide for unrestricted fluid flow through the ducts in the pistons to and from grooves 42, and their arrangement provides reversibility of the motor by reversing the pressure fluid supply and return.

Referring particularly to FIGS. 1 and 2, there are on the outer faces of stator plates 16f and l6r six circular indentations 74 which will be called pressure pads. These pressure pads are provided at their outer peripheries with O-ring seals 75 so that they form chambers between the stator plates and the cover plates. Each pressure pad 74 is connected by duct 76 to either an oil inlet port 70 or a low pressure return port 72. Pressure pads 74 compensate for and balance the internal fluid pressures which would otherwise tend to spread the stator plates away from the rotor faces. v

Still assuming counterclockwise rotation as seen in FIG. 3, high pressure supply fluid enters through the oil input coupling 78 in port end cover 6, from whence it is channeled by ducts 80 to the three pressure pads 74 which are connected to the three high pressure inlet ports 70a, 70b and 700. Low pressure return oil comes from the three pressure pads 74 which are connected to low pressure outlet ports 72a, 72b and 72c and thence via ducts 82 to return oil coupling 84.

The front stator plate 16f is identical to the rear plate l6r, both being anchored against rotation by suitable dowels 86 which permit the stator plates to move axially of the rotor. Since the parts fit closely, these movements are very slight, but nevertheless sufficient to effect good sealing of the stator plates against the rotor faces.

In operation, and still assuming counterclockwise rotation of the rotor as seen in FIG. 3, it will be apparent that piston 34a has retracted and is passing beneath flow abutment 44a. A few degrees counterclockwise of the 12 oclock position of piston 34a, it will be apparent that the inner end of its groove will crack into registry with high pressure inlet port 70a, and oil will start to flow through the axial duct 40 of the piston. High pressure oil which passes through a duct 76 in stator plate l6r passes through the cross bores 32 in rotor to the inner ends of corresponding radial grooves 30 in the front face 18f of the rotor (as well as the radial grooves 30 in the rear rotor face 164) and also into the opposite ports 70 in front stator plate 16f, through ducts 76 therein, and into pressure pads 74 between front stator plate 16f and drive end cover 8. The pressure of the fluid against the inner end of the piston, plus the drag on the piston caused by the oil flowing through its duct forces the piston radially outward. Its ball follows the undulating groove 36, and the piston designated 34b has at this time nearly fully extended. However, the preceding piston 340, by this time, has been fully extended and the expansion chamber at that instant lies between the piston 34c and the inclined end 62 of flow abutment 44. The pressure fluid supply for the expansion chamber is then through piston 34b. As piston 34c moves counterclockwise from the position shown in FIG. 3, it squeezes the fluid between it and the inclined end 60 of flow abutment 44b. This fluid forces against the outer end of piston 34d so as to force it inwardly. The fluid is exhausted through the axial duct 40 of piston 34d and flows from the inner end of this piston into the low pressure return fluid port 72a. The purpose of alcove 68 is to establish fluid communications between groove 42 and the outer ends of the pistons as the latter approach or leave a flow abutment, and while their outer ends are across grooves 42. Y

Leakage oil pressurizes the entire inner side of the motor casing, and this includes the area around the periphery of the rotor and that area between. the outer sides of the stator plates and the cover plates, outside the pressure pads.

Cavity pressure remains fixed at approximately 50 percent of the sum of inlet pressure plus outlet or exhaust pressure. If the motor is operated at 2,000 psi with an exhaust pressure of zero the cavity pressure approximates 1,000 psi. This 1,000 psi extends over the back surfaces of the stators (exclusive of pressure pads) and when added to the three pads under pressure provides area for perfect axial balancing. It also enables the application of the full line, high pressure oil, to the pads directly behind the high pressure areas within the rotor. This also provides a means to automatically pressure balance one, two, or three motor segments, depending on how many pressure pads (motor segments) are energized. Obviously with one inlet pressure pad and one outlet pressure pad for each motor segment, the overall pressure times area for these two pockets is going to equal one-half the total of inlet and exhaust pressure; this being the same as the cavity leakage pressure causes automatic balancing when the two are combined.

Assuming that high pressure oil is ported from the port cover into three pressure pads, the O-ring seals prohibit the oil from passing into the adjacent areas. These O-rings also act as a weak spring forcing the stator plated against the rotor. In addition, they fill the clearance gap between the stator plates and the port and drive covers; this reduces the need for close dimensional tolerances in the axial direction.

The oil is now forced into the rotor via the ports on the rotor side of the stator plate (ports opposite the balance pads on the stator plate). Within the rotor it flows into and through the pistons, does work in the expansible chamber formed on the ends by the radially extended piston and the abutment stops and on the sides by the stator plates. Then back into and through pistons into the low pressure ports. During this process some high pressure oil leaks directly across the abutment stops, some to the low pressure ports and the balance into the cavity or open area surrounding the rotor. If the unit is ideally axial-balanced, the side clearances will be held to a minimum with just enough clearance to provide a lubricating film of oil over these otherwise contacting and rubbing surfaces. The oil that leaks into the cavity from the high pressure areas on the faces of the rotor also leaks back from the cavity across the rotor faces to the low pressure areas. This pressure decrease, being a function of the differential pressure and land area involved, leaves the cavity pressure at one half the sum of the inlet and outlet pressures. This is due to the symmetry of the design necessary for motor rotational reversability.

The oil in the cavity which approximates one-half the sum of inlet and outlet pressure is permitted to fill the area behind the stator plate not being utilized for the pads. This oil cannot enter the low-pressure pockets from the external side because, again, the O-rings seal and separate these areas. The external, closing forces equal the internal, separation forces.

If no leakage existed between the rotor and the two stator faces then no pressure would exist externally to force these three components together. If this were to occur separation would result and leakage initiated. Conversely, when leakage does occur, pressure buildup behind the stator plates tends to close the clearance between the rotor and the two stator faces thereby resulting in reduced leakage. This results in an ideal hydrostatic (oil film) bearing between the facing surfaces. It is then possible to mechanically establish a leakage leading from the cavity to low pressure and guarantee oil passage across the faces concerned.

In the embodiment described, port cover 6 has been designed so that all three sections of the motor operate simultaneously, except in that the spacing of flow abutments is such that when, for example, piston 34a is in 12 oclock position directly beneath flow abutment 44a, the next corresponding piston 34a has passed the center next corresponding flow abutment, so that the three sections of the motor operate slightly out of phase with one another. By installing other port plates, with suitable channels or valving, the motor can be operated with only two sections charged or only one section charged, in which events the high pressure supply and low pressure return ports of the inactive section or sections should be connected to one another.

I claim:

1. A fluid motor comprising,

a hollow casing,

a spaced pair of stator plates with flat inner side faces,

a generally solid rotor mounted in said casing for rotation about an axis, said rotor having an annular outer periphery, and

substantially flat opposite side faces slidably engaging the inner side faces of said stator plates, each side face of the rotor having therein a plurality of angularly spaced radial grooves and an annular groove intersecting the radial grooves and disposed radially inward of the outer ends of the radial grooves, said rotor also having fluid passage means connecting the inner ends of the radial grooves pistons in said radial grooves slidable between an outwardly extended position in which outer ends thereof extend radially outward to at least the outer extremities of the annular grooves and an inwardly retracted position in which the outer ends thereof extend radially outwardly no farther than the inner extremities of the annular grooves, said pistons having fluid passage means therethrough,

a plurality of angularly spaced arcuate fluid abutments supported on each stator plate and slidably engaging in the annular grooves in the rotor side faces,

from end-to-end the inner side faces of the stator plates having therein undulant grooves extending for 360 in a substantially wave-form pattern in which radially inner runs thereof lie radially inward of the fluid abutments and in which radially outward runs thereof lie radially inward of the regions generally midway between abutment stops,

said pistons having thereof bearing members slidably engaging in said undulant grooves,

at least one of said stator plates having therein first and second sets of ports angularly spaced about a circle opposite the inner ends of the radial grooves on a side face of the rotor,

.the ports constituting one set being located on radii which are disposed towards corresponding ends of said fluid abutments and the ports constituting the other set being located on radii which are disposed towards corresponding opposite ends of said fluid abutments,

and means providing fluid conduits to said sets of 7 ports for the supply and return of motive fluid.

2. The combination claimed in claim 1, the sets of ports being in both stator plates, the means providing fluid conduits to said sets of ports including passages extending through said stator plates from the outer sides to the inner sides thereof,

the outer side of said stator plates having recesses therein larger than and communicating with said passages and constituting pressure pads.

3. The combination claimed in claim 1, said fluid abutments having arcuate inner and outer sides which face radially inward and outward with respect to the axis of rotation of the rotor, the outer sides of the abutments being substantially larger than the inner sides and being joined thereto by end walls which provide tapered end portions for said abutments.

4. The combination claimed in claim 3, said fluid abutments having limited freedom of radial movement and being supported on their respective stator plates by means of pins having shanks engaged in said stator plates and having shank-end portions engaged in slots in sides of said abutments, which slots extend radially with respect to the axis of rotation of said rotor.

5. The combination claimed in claim 4, said fluid abutments having cove means in the sides thereof which are opposite the slotted sides, whereby to increase the surface areas thereof so that pressure fluid will force the same against the stator plate on which they are supported.

6. The combination claimed in claim 1, the outer ends of said radial grooves extending outwardly beyond the outer extremities of said annular grooves,

the outer ends of said pistons in the extended positions thereof extending outwardly beyond the outer extremities of said annular grooves.

7. The combination claimed in claim 6, the inner sides of said stator plates having therein a pair of substantially L-shape recesses respectively adjacent to and between each pair of fluid abutments, said recesses each having a stern portion which lies opposite the annular groove in the adjacent rotor face and an arm portion extending from said stem portion in a direction away from the adjacent fluid abutment and which lies opposite the outer ends of the radial grooves in the rotor faces, whereby to provide fluid communication between the fluid passage means in the pistons and the annular grooves in the rotor faces when the pistons are in extended position.

8. A fluid motor comprising,

a hollow casing a spaced pair of stator plates in said casing having flat inner side faces,

a generally solid rotor mounted in said casing between stator plates for rotation about an axis,

said rotor having an outer periphery, and

substantially flat side faces slidably engaging said flat side faces of said stator plate, at least one of said flat side faces of the rotor having therein a plurality of angularly spaced radial grooves and an annular groove intersecting the radial grooves and disposed radially inward of the rotor periphery and the outer ends of the radial grooves,

pistons in said radial grooves slidable between an outwardly extended position in which outer ends thereof extend radially outward to at least the outer extremity of the annular groove and an inwardly retracted position in which the outer ends thereof extend radially outwardly no farther than the inner extremity of the annular groove, said pistons having fluid passage means therethrough,

a plurality of angularly spaced arcuate fluid abutments supported on the stator plate opposite the annular groove in the rotor and slidably engaging in the annular groove in the rotor side face,

the last-named side face of the stator plate having therein an undulant groove extending for 360 in a substantially wave-form pattern in which radially inner runs thereof lie radially inward of the fluid abutments and in which radially outward runs thereof lie radially inward of regions generally midway between abutments stops,

said pistons having thereof bearing members slidably engaging in said undulant grooves, said last-named stator plate having therein first and second sets of ports angularly spaced about a circle opposite the inner ends of the radial grooves on a side face of the rotor,

the ports constituting one set being located 0 radii which are disposed towards corresponding ends of said fluid abutments and the ports constituting the other set being located on radii which are disposed towards corresponding opposite ends of said fluid abutments,

and means providing fluid conduits to said sets of ports for the supply and return of motive fluid.

9. The combination claimed in claim'8, the means providing fluid conduits to said sets of ports including ducts extending through the last-named stator plate from the outer side to the inner side thereof,

the outer side of said last named stator plate having recesses therein larger than and communicating with said ducts and constituting pressure pads,

and a cap plate disposed on the outer side of the lastnamed stator plate and overlying said recesses and passages.

from end-to-end 10. The combination claimed in claim 8, said fluid abutment having arcuate inner and outer sides which face radially inward and outward with respect to the axis of rotation of the rotor, the outer sides of the abutments being substantially larger than the inner sides and being joined thereto by end walls which provide tapered end portions for said abutrnents.

11. The combination claimed in claim 10, said fluid abutments having limited freedom of radial movement and being supported on said one stator plate by pins having shanks engaged in said stator plate and having shank-end portions engaged in slots in sides of said abutments, which slots extend radially with respect to the axis of rotation of said rotor.

12. The combination claimed in claim 11, said fluid abutments having cove means in the sides thereof which are opposite the slotted sides, whereby to increase the surface areas thereof so that pressure fluid will force the same against said one stator plate.

13. The combination claimed in claim 8, the outer ends of said radial grooves extending outwardly beyond the outer extremity of said annular groove,

the outer ends of said pistons, in the extended positions thereof extending outwardly beyond the outer extremity of said annular groove.

14. The combination claimed in claim 13, the flat inner side of the last-named stator plate having therein a pair of substantially L-shape recesses respectively ad- 1 jacent to and between each pair of fluid abutments,

said recesses each having a stem portion which lies opposite the annular groove in the adjacent rotor face and an arm portion extending from said stem portion in a direction away from the adjacent fluid abutment and which lies opposite the outer ends of the radial grooves in the rotor faces, whereby to provide fluid communication between the fluid passage means in the pistons and the annular groove in the rotor flat face when the pistons are in extended position. 15. A fluid motor comprising, a hollow casing, a spaced pair of stator plates with flat inner side faces a generally solid rotor mounted in said casing between stator plates for rotation about an axis, said rotor having an outer periphery, and substantially flat opposite side faces slidably engaging the side faces of said stator plates, each side face of the rotor having therein a plurality of angularly spaced radial grooves and an annular groove intersecting the radial grooves and disposed radially inward of the outer ends of the radial grooves, said rotor also having 1 fluid passage means connecting the inner ends of the radial grooves, pistons in said radial grooves slidable between an outwardly extended position in which outer ends thereof extend radially outward to at least the outer extremities of the annular grooves and an inwardly retracted position in which the outer ends thereof extend radially outwardly no farther than the inner extremities of the annular grooves, said pistons having fluid passage means from end-to-end a plt i i gii iy i gularly spaced fluid abutments supported on each stator plate and slidably engaging in the annular grooves in the rotor side faces,

the inner side faces of the stator plates having therein undulant grooves extending for 360 in a substantially wave-form pattern in which radially inner runs thereof lie radially inward of the fluid abutments and in which radially outward runs thereof lie radially inward of the regions generally midway between abutment stops,

said pistons having thereof bearing members slidably engaging in said undulant grooves,

and means providing conduits for the supply and return of motive fluid to the inner ends of said radial grooves.

16. The combination claimed in claim 15, said stator plates being supported in said casing by means providing freedom of movement in the direction of the rotor axis, said casing including end cover plates having inner sides in flat face engagement with the outer sides of the stator plates, the means providing conduits for the supply and return of motive fluid including ducts through the stator plates which terminate at inner ends thereof in ports on the inner sides of the stator plates and which terminate at outer ends thereof in enlargements in the outer sides of the stator plates, and conduit means through one of said cover plates for con ducting motive fluid to and from said enlargements.

17. A fluid motor comprising, a rotor mounted for rotation about an axis, said rotor having an end face slidably engaging a face of a stator member, said end face having therein a plurality of angularly spaced radial grooves and an annular groove intersecting the radial grooves inwardly of the outer ends thereof, pistons slidable in said radial grooves, a plurality of angularly spaced fluid abutrnents supported on the stator member and slidably fitting in the annular groove in the rotor end race for dividing said annular groove into a plurality of arcuate working chambers, means providing for fluid passage lengthwise of the pistons from inner end portions of the pistons to and from outer end portions thereof, cam follower means on said pistons engaging cam groove means in said rotor face, said cam groove means having inner and outer runs disposed for reciprocating said pistons in said radial grooves between inwardly retracted positions angularly coinciding with said fluid abutments, in which retracted positions the outer ends of the pistons extend outwardly no farther than the inner extremity of the annular groove, and outwardly extended positions angularly coinciding with portions of said annular groove which lie between said fluid abutments, and in which outwardly extended positions the outer ends of the pistons extend outwardly of the annular groove, and conduits for the supply and return of motive fluid to and from the inner ends of the radial groove at locations angularly registering with opposite ends of said working chambers. 

1. A fluid motor comprising, a hollow casing, a spaced pair of stator plates with flat inner side faces, a generally solid rotor mounted in said casing for rotation about an axis, said rotor having an annular outer periphery, and substantially flat opposite side faces slidably engaging the inner side faces of said stator plates, each side face of the rotor having therein a plurality of angularly spaced radial grooves and an annular groove intersecting the radial grooves and disposed radially inward of the outer ends of the radial grooves, said rotor also having fluid passage means connecting the inner ends of the radial grooves pistons in said radial grooves slidable between an outwardly extended position in which outer ends thereof extend radially outward to at least the outer extremities of the annular grooves and an inwardly retracted position in which the outer ends thereof extend radially outwardly no farther than the inner extremities of the annular grooves, said pistons having fluid passage means from end-to-end therethrough, a plurality of angularly spaced arcuate fluid abutments supported on each stator plate and slidably engaging in the annular grooves in the rotor side faces, the inner side faces of the stator plates having therein undulant grooves extending for 360* in a substantially waveform pattern in which radially inner runs thereof lie radially inward of the fluid abutments and in which radially outward runs thereof lie radially inward of the regions generally midway between abutment stops, said pistons having thereof bearing members slidably engaging in said undulant grooves, at least one of said stator plates having therein first and second sets of ports angularly spaced about a circle opposite the inner ends of the radial grooves on a side face of the rotor, the ports constituting one set being located on radii which are disposed towards corresponding ends of said fluid abutments and the ports constituting the other set being located on radii which are disposed towards corresponding opposite ends of said fluid abutments, and means providing fluid conduits to said sets of ports for the supply and return of motive fluid.
 2. The combination claimed in claim 1, the sets of ports being in both stator plates, the means providing fluid conduits to said sets of ports including passages extending through said stator plates from the outer sides to the inner sides thereof, the outer side of said stator plates having recesses therein larger than and communicating with said passages and constituting pressure pads.
 3. The combination claimed in claim 1, said fluid abutments having arcuate inner and outer sides which face radially inward and outward with respect to the axis of rotation of the rotor, the outer sides of the abutments being substantially larger than the inner sides and being joined thereto by end walls which provide tapered end portions for said abutments.
 4. The combination claimed in claim 3, said fluid abutments having limited freedom of radial movement and being supported on their respective stator plates by means of pins having shanks engaged in said stator plates and having shank-end portions engaged in slots in sides of said abutments, which slots extend radially with respect to the axis of rotation of said rotor.
 5. The combination claimed in claim 4, said fluid abutments having cove means in the sides thereof which are opposite the slotted sides, whereby to increase the surface areas thereof so that pressure fluid will force the same against the stator plate on which they are supported.
 6. The combination claimed in Claim 1, the outer ends of said radial grooves extending outwardly beyond the outer extremities of said annular grooves, the outer ends of said pistons in the extended positions thereof extending outwardly beyond the outer extremities of said annular grooves.
 7. The combination claimed in claim 6, the inner sides of said stator plates having therein a pair of substantially L-shape recesses respectively adjacent to and between each pair of fluid abutments, said recesses each having a stem portion which lies opposite the annular groove in the adjacent rotor face and an arm portion extending from said stem portion in a direction away from the adjacent fluid abutment and which lies opposite the outer ends of the radial grooves in the rotor faces, whereby to provide fluid communication between the fluid passage means in the pistons and the annular grooves in the rotor faces when the pistons are in extended position.
 8. A fluid motor comprising, a hollow casing a spaced pair of stator plates in said casing having flat inner side faces, a generally solid rotor mounted in said casing between stator plates for rotation about an axis, said rotor having an outer periphery, and substantially flat side faces slidably engaging said flat side faces of said stator plate, at least one of said flat side faces of the rotor having therein a plurality of angularly spaced radial grooves and an annular groove intersecting the radial grooves and disposed radially inward of the rotor periphery and the outer ends of the radial grooves, pistons in said radial grooves slidable between an outwardly extended position in which outer ends thereof extend radially outward to at least the outer extremity of the annular groove and an inwardly retracted position in which the outer ends thereof extend radially outwardly no farther than the inner extremity of the annular groove, said pistons having fluid passage means from end-to-end therethrough, a plurality of angularly spaced arcuate fluid abutments supported on the stator plate opposite the annular groove in the rotor and slidably engaging in the annular groove in the rotor side face, the last-named side face of the stator plate having therein an undulant groove extending for 360* in a substantially wave-form pattern in which radially inner runs thereof lie radially inward of the fluid abutments and in which radially outward runs thereof lie radially inward of regions generally midway between abutments stops, said pistons having thereof bearing members slidably engaging in said undulant grooves, said last-named stator plate having therein first and second sets of ports angularly spaced about a circle opposite the inner ends of the radial grooves on a side face of the rotor, the ports constituting one set being located on radii which are disposed towards corresponding ends of said fluid abutments and the ports constituting the other set being located on radii which are disposed towards corresponding opposite ends of said fluid abutments, and means providing fluid conduits to said sets of ports for the supply and return of motive fluid.
 9. The combination claimed in claim 8, the means providing fluid conduits to said sets of ports including ducts extending through the last-named stator plate from the outer side to the inner side thereof, the outer side of said last named stator plate having recesses therein larger than and communicating with said ducts and constituting pressure pads, and a cap plate disposed on the outer side of the last-named stator plate and overlying said recesses and passages.
 10. The combination claimed in claim 8, said fluid abutment having arcuate inner and outer sides which face radially inward and outward with respect to the axis of rotation of the rotor, the outer sides of the abutments being substantially larger than the inner sides and being joined thereto by end walls which provide tapered end portions for said abutments.
 11. The combination claimed in claim 10, said fluid abutments having limited freedom of radial movement and being supported on said one stator plate by pins having shanks engaged in said stator plate and having shank-end portions engaged in slots in sides of said abutments, which slots extend radially with respect to the axis of rotation of said rotor.
 12. The combination claimed in claim 11, said fluid abutments having cove means in the sides thereof which are opposite the slotted sides, whereby to increase the surface areas thereof so that pressure fluid will force the same against said one stator plate.
 13. The combination claimed in claim 8, the outer ends of said radial grooves extending outwardly beyond the outer extremity of said annular groove, the outer ends of said pistons, in the extended positions thereof extending outwardly beyond the outer extremity of said annular groove.
 14. The combination claimed in claim 13, the flat inner side of the last-named stator plate having therein a pair of substantially L-shape recesses respectively adjacent to and between each pair of fluid abutments, said recesses each having a stem portion which lies opposite the annular groove in the adjacent rotor face and an arm portion extending from said stem portion in a direction away from the adjacent fluid abutment and which lies opposite the outer ends of the radial grooves in the rotor faces, whereby to provide fluid communication between the fluid passage means in the pistons and the annular groove in the rotor flat face when the pistons are in extended position.
 15. A fluid motor comprising, a hollow casing, a spaced pair of stator plates with flat inner side faces a generally solid rotor mounted in said casing between stator plates for rotation about an axis, said rotor having an outer periphery, and substantially flat opposite side faces slidably engaging the side faces of said stator plates, each side face of the rotor having therein a plurality of angularly spaced radial grooves and an annular groove intersecting the radial grooves and disposed radially inward of the outer ends of the radial grooves, said rotor also having fluid passage means connecting the inner ends of the radial grooves, pistons in said radial grooves slidable between an outwardly extended position in which outer ends thereof extend radially outward to at least the outer extremities of the annular grooves and an inwardly retracted position in which the outer ends thereof extend radially outwardly no farther than the inner extremities of the annular grooves, said pistons having fluid passage means from end-to-end therethrough, a plurality of angularly spaced fluid abutments supported on each stator plate and slidably engaging in the annular grooves in the rotor side faces, the inner side faces of the stator plates having therein undulant grooves extending for 360* in a substantially wave-form pattern in which radially inner runs thereof lie radially inward of the fluid abutments and in which radially outward runs thereof lie radially inward of the regions generally midway between abutment stops, said pistons having thereof bearing members slidably engaging in said undulant grooves, and means providing conduits for the supply and return of motive fluid to the inner ends of said radial grooves.
 16. The combination claimed in claim 15, said stator plates being supported in said casing by means providing freedom of movement in the direction of the rotor axis, said casing including end cover plates having inner sides in flat face engagement with the outer sides of the stator plates, the means providing conduits for the supply and return of motive fluid including ducts through the stator plates which terminate at inner ends thereof in ports on the inner sides of the stator plates and which terminate at outer ends thereof in enlargements in the outer sides of the stator plates, and conduit means through One of said cover plates for conducting motive fluid to and from said enlargements.
 17. A fluid motor comprising, a rotor mounted for rotation about an axis, said rotor having an end face slidably engaging a face of a stator member, said end face having therein a plurality of angularly spaced radial grooves and an annular groove intersecting the radial grooves inwardly of the outer ends thereof, pistons slidable in said radial grooves, a plurality of angularly spaced fluid abutments supported on the stator member and slidably fitting in the annular groove in the rotor end race for dividing said annular groove into a plurality of arcuate working chambers, means providing for fluid passage lengthwise of the pistons from inner end portions of the pistons to and from outer end portions thereof, cam follower means on said pistons engaging cam groove means in said rotor face, said cam groove means having inner and outer runs disposed for reciprocating said pistons in said radial grooves between inwardly retracted positions angularly coinciding with said fluid abutments, in which retracted positions the outer ends of the pistons extend outwardly no farther than the inner extremity of the annular groove, and outwardly extended positions angularly coinciding with portions of said annular groove which lie between said fluid abutments, and in which outwardly extended positions the outer ends of the pistons extend outwardly of the annular groove, and conduits for the supply and return of motive fluid to and from the inner ends of the radial groove at locations angularly registering with opposite ends of said working chambers. 